fix: case-sensitive label matching broken on PostgreSQL

syncLabels created Labels with original case (e.g. "Projet") but
searched with .toLowerCase() (e.g. "projet"). On PostgreSQL (case-
sensitive), findMany returned [] → labelRelations disconnected →
orphan cleanup deleted ALL notebook labels.

Fix: use Prisma mode:'insensitive' for findFirst and findMany,
deduplicate case-insensitively while preserving original case.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

memento-note/app/actions/notes.ts

@@ -107,12 +107,22 @@ async function syncLabels(userId: string, noteLabels: string[] = [], notebookId?
     const nbScope = notebookId ?? null
 
     if (noteLabels.length > 0) {
-      const trimmedNames = [...new Set(
+      // Deduplicate case-insensitively, keep original case
-        noteLabels.map(name => name?.trim()).filter((n): n is string => Boolean(n))
+      const seen = new Set<string>()
-      )]
+      const trimmedNames = noteLabels
+        .map(name => name?.trim())
+        .filter((n): n is string => Boolean(n))
+        .filter(n => {
+          const key = n.toLowerCase()
+          if (seen.has(key)) return false
+          seen.add(key)
+          return true
+        })
+
       for (const name of trimmedNames) {
+        // Case-insensitive find on PostgreSQL
         const existing = await prisma.label.findFirst({
-          where: { userId, name, notebookId: nbScope },
+          where: { userId, name: { equals: name, mode: 'insensitive' }, notebookId: nbScope },
         })
         if (!existing) {
           await prisma.label.create({
@@ -120,14 +130,16 @@ async function syncLabels(userId: string, noteLabels: string[] = [], notebookId?
           })
         }
       }
+
+      if (trimmedNames.length === 0) return []
+      // Search with original case (case-insensitive on PostgreSQL)
+      return prisma.label.findMany({
+        where: { userId, notebookId: nbScope, name: { in: trimmedNames, mode: 'insensitive' } },
+        select: { id: true, name: true },
+      })
     }
 
-    if (noteLabels.length === 0) return []
+    return []
-    const uniqueNames = [...new Set(noteLabels.map(n => n.trim().toLowerCase()).filter(Boolean))]
-    return prisma.label.findMany({
-      where: { userId, notebookId: nbScope, name: { in: uniqueNames } },
-      select: { id: true, name: true },
-    })
   } catch (error) {
     console.error('Fatal error in syncLabels:', error)
     return []